This invention relates to emulsions of polymeric materials. In another aspect, this invention relates to novel stable emulsions formed with ethylene homopolymers and copolymers. Still another aspect of this invention relates to novel stable polymeric emulsions which are particularly suitable as prime ingredients in formulations used to coat solid materials such as latex paints and polishes.
Various polymeric emulsions are known in the art which are used in coatings, lacquers, paints, and polishes. For example, polyethylene emulsions are commonly used as the wax component in polish formulations. Eary polyethylene emulsions which were utilized in liquid emulsion polishes, for example, were made from polyethylenes which were oxygenated. Such polyethylenes were produced by telomerization of ethylene and subsequent oxidation of the telomer, or by thermal degradation of high molecular weight polyethylenes to low molecular products which are then oxidized as disclosed in U.S. Pat. Nos. 2,964,487 and 2,928,797. The hydrophilic oxygenated groups on the resulting oxidized polymeric particles allowed them to be emulsified. These emulsions rarely had a molecular weight more than about 3000 but formed smooth films when they were dried upon a surface. However, the oxygenated polyethylene materials have a disagreeable odor which taints the emulsions prepared therefrom and the products which contain such emulsions such as liquid polishes. Furthermore, these materials often have a yellow tinge.
In an attempt to form polyethylene particles in emulsion which have improved mechanical properties of toughness durability and hardness but which do not have the inherent disagreeable odor or color, emulsion polymerization processes were developed to produce relatively high molecular weight materials having relatively small particle size. Stable polyethylene latexes comprising polyethylene solids have been produced by polymerizing ethylene at elevated temperatures and pressures in an aqueous reaction medium containing an emulsifying agent and an initiator. Generally, the emulsion formed polymers have lower molecular weight than non-emulsion formed ethylene polymers produced by conventional high pressure processes but a higher molecular weight than the above described oxygenated polyethylenes.
Improved stable polyethylene emulsions which have found satisfactory use in various coatings, lacquers, paints and polishes comprise polyethylene solids of increased hardness, relatively high molecular weight, and relatively small particle size which have been produced by emulsion polymerization techniques such as set forth in U.S. Pat. Nos. 3,226,352 and 3,244,652. Examples of such polyethylene emulsions used in polish formulations are set forth in U.S. Pat. No. 3,247,141. These emulsion polymerized polyethylenes have molecular weights ranging from about 7,000 to 40,000 and particle sizes ranging broadly from around 200 angstroms to about 5000 angstroms, with the average particle size of most emulsion produced polyethylenes being 500 angstroms and greater. The use of these emulsions has eliminated the disagreeable odor and color characteristics which were inherent in the oxidized polyethylenes, and produced performance in spreading, leveling, gloss, water spot resistance, buffability and removability which is comparable to the oxidized polyethylenes. However, such conventional emulsion polmerized polyethylenes have not been utilized in as wide a variety of applications as desired because incompatibility problems exist when they are admixed with certain standard formulations of paints and polishes, causing precipitation of solids and other instability problems. Thus, there is a need for emulsions of ethylene polymers which are extremely stable and compatible with various types of latexes, admixtures, and formulations which are utilized in coating applications including paints and polishes.